The invention relates to a corpuscular beam microscope such as electron microscopes in general and more particularly to such a microscope with adjusting means for changing the position of the object to be imaged relative to the equipment axis and/or relative to the focusing plane of the objective lens on the specimen side and/or for changing the position of the image of the object relative to the equipment axis.
Adjusting means for changing the position of the object to be imaged relative to the equipment axis are to be understood herein as the usual devices which serve for the mechanical displacement of the object (specimen) or the object carrier in the horizontal direction, e.g. in two coordinates (x, y). It is known to drive such adjusting devices using motors (German Pat. Nos. 1,564,657 and 1,614,528). To change the position of the object relative to the focusing plane on the specimen side, it is possible to either change the excitation of the objective lens or raise or lower the object mechanically along the equipment axis (e.g., German Pat. No. 1,514,595). Displacement of the object image relative to the equipment axis can be accomplished by a deflection system arranged below the objective lens (Siemens Publication Eg 1/204, January, 1969).
Where photographic recording of the image is to be carried out, the effective resolution of corpuscular beam microscopes depends decisively on the quietness of the picture; the latter, in turn, is the better with better regulation of the electrical operating parameters. In particular, such is accomplished when the beam voltage and the lens currents are regulated for constancy and the less the object itself moves. In principle, the electrical operating parameters can be controlled using proper control circuits, but thermal motion (drift) of the object can hardly be avoided, particularly if the object is cooled or heated. In high resolution electron microscopes a position stability of the object of, at best, on the order of 0.1 A/s is achieved.